Patent GB-341899-A (GB)
Title: Manufacture of artificial threads and other products from cellulose compounds
IPC: D06M11/53
Filed: 1929-07-19
Abstract: Coatings and other materials produced by the processes of the parent Specification, and Specifications 335,993, [Class 95, Paints &c.], and 341,930 are desulphurized by treating with warm or hot alkali sulphide solution containing at least 5 per cent of alkali sulphide calculated as Na2S; 9 H2O, or with an equivalent strength of alkali hydrosulphide.  The treatment removes any yellow colouration or opalescence in the materials as first prepared.  It may be carried out on the freshly prepared material or after finishing and drying in the ordinary way.  The material may be treated in stretched or non-stretched condition. The treatment may precede or follow a bleaching process, but the latter may be dispensed with if the alkali sulphide is sufficiently strong.  The tenacity is said to be increased in many cases, and the treatment may be applied to material which at the time of formation or after treatment with ordinary weak sulphide solutions and bleaching, is not yellow or opalescent.  The strength of the alkali sulphide may be varied considerably, for example from 5 to 58 per cent.  Specification 274,521, [Class 2 (ii), Cellulose &c.], also is referred to.ALSO:Artificial silk, films, bands, plates, dressings, coatings and the like produced by the processes of the parent Specification, and Specifications 335,993, [Class 2 (ii), Cellulose &c.], and 341,930, are desulphurized by treating with warm or hot alkali sulphide solution containing at least 5 per cent of alkali sulphide, calculated as Na2S; 9H2O, or with alkali hydrosulphide of equivalent strength.  The treatment removes any yellow colouration or opalescence in the material as first prepared.  It may be carried out on the freshly formed material or after finishing and drying in the normal way.  The treatment may take place before or after a bleaching process but the latter may be dispensed with if the alkali sulphide solution is sufficiently strong.  The material may be treated in stretched or non-stretched condition.  The treatment is stated to increase the tenacity of the material in many cases.  In the examples, artificial silk, made according to certain of the examples of the parent Specification, which resists the action of ordinary weak desulphurizing baths, is introduced in unbleached undesulphurized condition into 30 per cent sodium sulphide solution at 100 DEG  C. and after 2 minutes is rinsed with hot and cold water and dried.  The treated silk is rendered pure white with increased lustre.  The strength of the alkali sulphide may be varied from 5 to 58 per cent and the time of treatment may be increased when using the lower concentrations of alkali sulphide. After washing out the alkali sulphide, the silk may be treated with dilute sulphuric acid before the final washing.  The process may be applied to products which are white at the time of formation or after desulphurizing and bleaching in the ordinary way, in order to impart to them a softer feel.  Specification 274,521, [Class 2 (ii), Cellulose &c.], also is referred to.ALSO:Containing cellulose xanthates and ethers.-Plates, bands, dressings, coatings and the like produced by the processes of the parent Specification, and Specifications 335,993, [Class 70, Indiarubber &c.], and 341,930, are desulphurized by treating with warm or hot alkali sulphide solution containing at least 5 per cent of alkali sulphide, calculated as Na2S; 9H2O, or with alkali hydrosulphide of equivalent strength.  The treatment removes any yellow colouration or opalescence in the material as first produced.  It may be carried out on the freshly formed material or after finishing and drying in the ordinary way. The treatment may take place before, during or after a bleaching process but the latter may be dispensed with if the alkali sulphide is sufficiently strong.  The material may be treated in stretched or non-stretched condition.  The treatment is stated to increase the tenacity of the material in many cases, and it may be applied to products, which are not yellow or opalescent at the time of formation or after treating with the ordinary weak sulphide solutions and bleaching.  The strength of the alkali sulphide may be varied considerably, for example, from 5 to 58 per cent.  Specification 274,521, [Class 2 (ii), Cellulose &c.], also is referred to.